As refrigerant circuitry for an air conditioning system, two-system refrigerant circuitry, such as that disclosed in Japanese Laid-Open Publication No. 62-238951, has conventionally been known. Refrigerant circuitry of this type includes: a primary refrigerant circuit in which a compressor, a heat exchanger on the first heat source side, a pressure reducing mechanism and a heat exchanger on the first application side are sequentially connected to each other through a refrigerant pipe; and a secondary refrigerant circuit in which a pump, a heat exchanger on the second heat source side and a heat exchanger on the second application side are connected to each other through a refrigerant pipe.
And, heat is exchanged between the heat exchanger on the first application side of the primary refrigerant circuit and the heat exchanger on the second heat source side of the secondary refrigerant circuit, and the heat exchanger on the second application side is disposed within a room to be air-conditioned.
In this refrigerant circuitry, during the room cooling running, a refrigerant is evaporated in the heat exchanger on the first application side and the refrigerant is condensed in the heat exchanger on the second heat source side. The condensed refrigerant exchanges heat with the indoor air in the heat exchanger on the second application side and is evaporated, thereby cooling the indoor air.
On the other hand, during the room heating running, a refrigerant is condensed in the heat exchanger on the first application side and the refrigerant is evaporated in the heat exchanger on the second heat source side. The evaporated refrigerant exchanges heat with the indoor air in the heat exchanger on the second application side and is condensed, thereby heating the indoor air.
In this way, the piping length of the primary refrigerant circuit is shortened, thereby trying to improve the refrigerating capacity.
However, in such an arrangement, a pump is required as a discrete driving source for circulating the refrigerant in the secondary refrigerant circuit. As a result, the power consumption and the like are increased. In addition, since such a driving source is required, the number of parts having such factors as to cause some failure is increased and thus the reliability of the entire system is adversely deteriorated.
As refrigerant circuitry for overcoming these problems, there exists a heat transport system of a so-called "non-powered" heat transport type, in which no driving source is provided for the secondary refrigerant circuit. Heat transport systems of such a type include a system disclosed in Japanese Laid-Open Publication No. 63-180022. In the heat transport system, a secondary refrigerant circuit is constructed such that a heater, a condenser and a sealed container are sequentially connected to each other through a refrigerant pipe and that the sealed container is disposed at a position higher than that of the heater. Moreover, the heater and the sealed container are connected to each other through an equalizer pipe including an opening/closing valve.
According to such an arrangement, during the room heating running, the opening/closing valve is first closed. A gaseous refrigerant heated by the heater is condensed in the condenser so as to be liquefied. Then, the liquid refrigerant is recovered into the sealed container. Thereafter, the opening/closing valve is opened, the pressure in the heater is equalized by the equalizer pipe with the pressure in the sealed container, and then the liquid refrigerant is recovered from the sealed container, disposed at a position higher than that of the heater, to the heater.
By repeating this operation, the circulation of the refrigerant is enabled without providing any driving source such as a pump for the secondary refrigerant circuit.
(Problems to be Solved)
However, in such a heat transport system, if the gaseous refrigerant flows from the condenser into the sealed container, then the pressure in the sealed container rises. As a result, there is some possibility that the operation of circulating the refrigerant cannot be performed satisfactorily. Thus, the refrigerant needs to be excessively cooled in the condenser so that the gaseous refrigerant does not flow out from the condenser.
Moreover, the heat transport system ameliorates the inner structure of the sealed container so as to suppress a rise in pressure within the sealed container. However, the system cannot be regarded as attaining sufficient reliability.
Furthermore, if the liquid refrigerant is to be introduced into the sealed container with certainty in this manner, then the condenser is required to be disposed at a position higher than that of the sealed container. Thus, since undue restriction is imposed on the positions where the respective units are disposed, it is difficult to apply such a system to a large-scale system or a system having a long pipe.
In view of this point, the present invention has been devised in order to accomplish an objective of alleviating the restriction on the positions where the units are disposed and attaining high reliability and universality for a heat transport system of a non-powered heat transport type requiring no driving source.